Electric elevator system



G. B. GROSV ENOR ELECTRIC ELEVATOIi SYSTEM 'Dec'. 22 J 1925.

Filed March '7. 1922 2 Sheets-Sheet 1 INVE/VTUR firmkwm- 45. b

G. B. GROSVENOR ELECTRIC ELEVATOR SYSTEM Dec. .22 T, 1925.

Filed March 7. 1922 2 Sheets-Sheet 2 U AUX 8 I o J Dhllb 12 w d E k 6 g a a w J S l W E J J x m, E 4 m J M INVENTOR MW Patented Dec. 22, 1925.

UNITED STATES 1,566,399 PATENT OFFICE.

GRAHAM B. GROSVENOR, OF CHICAGO, ILLINOIS, ASSIGNOR TO OTIS ELEVATOR COM- PANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ELECTRIC ELEVATOR SYSTEM.

Application filed March 7, 1922. Serial No. 541,815.

To all whom it may concern.-

Be it known that I, GRAHAM B. Gnos- VENOR, a citizen of the United States, and a resident of Chicago, county of Cook, State of Illinois, have invented certain new and useful Improvements in Electric Elevator Systems, of which the followingis a specification.

My invention relates to electric elevator systems, and more particularly to such systems as are used for high speed elevators.

In elevator systems operating cars at speeds of say four hundred to seven hun- (lred feet per minute, the time required to accelerate and retard the cars between stops may often determine the practicability of the system used. It is important that, in addition to a high rate of acceleration and retardation, the changes in speed shall be uniform and smooth. It is also important that the devices used shall be simple and rugged and that the operator in the elevator car shall have easy and accurate control of its movements.

Several systems have been proposed for controlling the direction and speed characteristics of elevators. VV-ard Leonard, in which the elevator motor is supplied with current from a generator driven by a second motor. The elevator motor has a separately ezicited field of constant strength and the up or down direction of the elevator is secured by properly selecting the direction of the current through the generator field while the speed is varied by varying-the strength of the generator field. The generator armature and elevator motor armature are always electrically connected.

Another system is the type used in connection with a power supply of constant voltage. In this system, change of direction is accomplished by reversing the current in the armature circuit of the elevator motor while maintaining the field always of the same polarity. The acceleration of the elevator is affected by varying a resistance in the armature circuit of the elevator motor.

Still another system involves the use of Among these, is the' voltage to another. This system requires a motor and a plurality of generators driven thereby for producing the number of voltages required (usually tour) so is principally used in connection with a bank of elevator-s.

One object of my present invention is to provide an elevator system that will permit of a high average speed, that will give rapid and smooth acceleration and retarda-- tion, and that will enable the car to be handled by the operator with ease and accuracy. Another object is to provide an improved system in which the elevator motor may be run directly from the main supply line when the elevator is running at full speed and from a generator at all other times.

elevators, one motor may drive all gener-.

ators). The generator operates at a plurality of fixed voltages obtained by varying the field current, but the polarity is always the same. The speed of the elevator depends on the voltage applied at the elevator motor armature terminals and the acceleration is limited by the rate at which the generator field builds up. Change of direction of the elevator is accomplished by reversing the armature current of the'elevator motor. To stop the elevator, the circuit of the elevator motor armature is disconnected from the generator and the elevator brought to rest by the dynamic braking action of a resistance thrown across the terminals of the elevator motor armature. When brought to rest, the elevator is held by an el ctromechanical brake until such time as c rrent is again supplied to the elevator mot r armature. In certain embodiments, when the elestant voltages.

obtained by switching from one Xed vator hasbeen brought up to nearly full speed, the elevator motor may be connected directly across the line supplying the driving motor and the generator will then be floating on the line, together with the motor driving it.

a current-supply having a plurality of con- The elevator motor field is always of one polarity and change of direc- -isiaccomplished by reversing the curntli'n'jthe armature. Variations in s eed in parallel.

In order that my invention may be fully understood, it is described in connection.

with the which Figure 1 is a diagrammatic view showing the principal elements of my system.

Figure 2 is a wiring diagram of av system for one elevator.

Figure 3 is a. wiring diagram showing an adaptation for a plurality of elevators.

Referring more particularly to the drawings, elevator car 1, Figure 1, is supported by cable 2, which passes over traction wheel 3 and is attached to counterweight 4. Traction wheel 3 is secured to shaft 5, to which are also fastened the armature 6 of the elevator motor 7 and the brake pulley 8 of an electromechanical brake 9. /Vire 10 connects one terminal of the elevator motor armature 6 with the diagonally opposite contacts 11 and 12 of the reversing switch 13. Wire 14 connects the other terminal of armatures 6 to the contacts 15 and 16 of the reversing switch 13. The center contacts 17 and 18 of reversing switch 13 are connected with the terminals of the generator armature 19 by wires 20 and 21 respectively. Series field coil 22 for the generator 23 is included in this circuit. Armature 19 is driven through shaft 24 by armature 25 of the driving motor 26. Motor 26 may be D. C. or A. C. of any type that will maintain substantially constant speed at all loads, here shown by way of example as a shunt motor, the field coils 27 of which are connected across the supply 'main. In addition to series field 22, generator 23 is provided with a separately excited field winding 28 supplied with a direct current through wires 29 and 30. A resistance 31 is included in the circuit of field winding 28 and a switch 32 for short-circuiting the resistance 31 has its contacts connected to the two ends of the resistance. Elevator motor 7 has a separately excited field winding 33, supplied from a direct current source throu'yh wires 34 and 35, in the latter of which is inserted resistance 36. Switch 37 is adapted to shortcircuit resistance 36. An electromechanical brake is shown diagrammatically at 9, which is intended to represent any well known construction in which a solenoid is energized to disengage the brake and a spring acting against the pull of the solenoid applies the brake when the solenoid is deenergized. lVinding 38 of the solenoid of brake 9 is supplied with current through the wires 39 and 40. A circuit including a resistance 41 and switches 42 and 43, having their gaps in series, is shunted across the terminals of the solenoid winding 38. In the Wire 40 are the switches 44 and 45 having their gaps Across the terminals of the armature 6 of elevator motor 7 is connected a low resistance 46 and a switch 47 Resistaccompanyingdrawings,

ance 46 serves as an electro-dynamic brake when switch 47 is closed.

The operation of my system as described above is as follows :-The driving motor 26 and generator. 23 run continuously during the period over which it is desired to run the elevator and at as nearly constant speed as is practicable. It will be understood that all the switches of Figure 1 are controlled by the operator in the elevator car. Assume ing that reversing switch 13 is open, the elevator is at rest and the switches are all as shown in Figure 1. It is to be noted that switches 42 and 43 are closed and switches 44 and 45 are open so that solenoid winding 38 is deenergizcd and brake 9 is being applied to hold the elevator stationary. Also that switch 47 is closed, but the dynamic brake will not act when the elevator is at rest. Switch 37 is closed and therefore full field strength is on elevator motor 7. This gives maximum torque for starting. Field winding 28 of generator 23 is connected to the line through resistance 31, since switch 32 is open. Therefore, a certain low voltage .1

is being developed at the terminals of the generator armature 19. Resistance 31 is adjusted to produce a voltage that will give the desired slow speed for the elevator and l have found that, when using 240 volts as the voltage corresponding to full speed of the elevator, very good operation is secured when this low voltage is approximately 40 volts. 1

To start the elevator in the up direction, reversing switch 13 is thrown so that contacts 17 and 18 are connected to contacts 16 and 12, as shown by dotted lines. Simultaneously with the closing of reversing switch 13, switch 44 is closed and switch 43 opened, so that solenoid 38 of brake 9 is energized and the brake disengaged. Switch 47 is also opened .simultaneously with the closing of the reversing switch 13. It is thus seen that the low voltage is applied to the terminal of the elevator motor armature 6 when it is at rest and the resistance of the elevator motor armature 6 must be such as to prevent an excessive rush of current at starting. There may be considerable variation in the load 011 the elevator motor 7, due to the number of passengers, with a consequent tendency to variation in speed. A uniform low speed of the elevator is very important as it is from this speed that stops are made and the operator can register the elevator platform with the landing sill with great accuracy and without inching if the speed is constant. The designs of the generator 23 and motor 7 are chosen to give this desired uniform slow speed and among the chief features of such design is the use of a properly adjusted series field 22 of the generator 23.

When the elevator has been brought from lll'.)

rest to low speed, (which can be done in a fraction of a second, due to the fact that the amount of energy involved is low), it is then brought to its normal full speed by closing switch 32, thereby short-circuiting the resistance 31 and increasing-the generator voltage to its full value. The rate of acceleration of the elevator will depend on the time required to build up the generator field and this can be provided for by the design of the generator. Further, the time required to build up the field from the fixed low voltage value to the maximum voltage value is considerably less than would be required to build the full field strength t'ron' zero value. it it is desired to bring the cle vator from rest to normal full speed as quickly as possible, switch 32 is closed immediately after the operations requ red to give low speed are completed,-as described above, and the time required to accelerate the elevator then depends on the time'required to build up the generator field. It is apparent that the acceleration will to smooth, which is impossible in systems involving the cutting out of resistance in steps or the application of successively higher voltages 'to the elevator motor in steps.

Further, as the actuation of the switches to cut out resistance step by step is ell'ected by solenoids in which a time element always enters, a more rapid acceleration is possible by my system, as well as a more simple construction. v

When the elevator has been brought to full normal speed, switch 87 may be opened automatically, as shown for example in an embodiment to be subsequently described, and the speed of the elevator still further increased. This results from the weakening of the motor field by the introduction of the resistance 36. In certain cases, the switch 37 may be opened simultaneously with the closing of switch 32, as the chief object of the strong motor field is to give a large starting torque.

Assuming that it is desired to bring the elevator from full speedto low speed, the switch 32 is opened and the resistance 31 is again in the circuit of the generator field. The generator will then act as a motor supplied with current from the elevator motor,

which will act as a generator until the speed of the elevator motor has decreased to a point where the voltage equals that of the generator corresponding to the lowspeed voltage. The elevator will then continue to run at the low speed. If it is now desired to stop the elevator, reversing switch 13 is opened, thus disconnecting the elevator motor from the generator, and simultaneously switch 47 is closed. switch 44 opened and switch 42-, closed. The closing of switch- 47 places the resistance 46 across the terminals of the elevator motor armature 6 and electro-dynamic braking ensues. At the same time, solenoid winding 38 has been disconnected from the line by the opening of switch 44 and connected to the resistance 41, through which it discharges. This results in a delayed action of the electromechanical brake 5) so that it is fully applied only at the time the elevator comes to rest and the dynamic braking action of resistance 4(5 ceases. The retardation is, therefore, smoothand uniform and accurate stops may be made.

The elevator may be equally well brought- "0 rest from full speed by opening switch :32 at the same time as switch 1;, is opened, switch 4-? closed, switch 44 opened, and switch 43 closed, that is, by combining the operations required to bring the elevator to low speed and to bring it to rest from low speed.

It will be umlerstood that to run the elevator in the down direction, the proper switches are operated in a similar manner to that just described; thus to get low speed in the down direction, revm'sing switch 13 is thrown to connect contacts 17 and 18 with contacts 11 and to apply the low voltage, switch 4:) is closed. and switch 42 pcned to release brake 9, and switch 47 opened to disconnect resistance 46 across the terminals of armature 6.

In Figure 2, a shunt motor armature 50 ot' the driving motor is shown connected by wires 51 and 52 to the mains 53 and 54 ot' a supply line connected to a source of direct current power through switch 55. Field winding 56 is connected across wires 51 and 52 and the usual starting resistance 57 is included in the circuit of armature 50. Motor 58 drives the armature 59 of the generator (30, as already shown and described in connection with Figure 1. This motorgenerator set preterably is located in the motor room and runs continuously while the elevator is in service. The field coil 61 is connected in series with the resistance 62 across the mains 53 and 54 by the wires 63 and 64. The armature G!) of the elevator motor 66 drives a t'action wheel (see Figure 1) over which the elevator cable runs. Motor 66 is also located in the m0- tor room which is preferably at the top of the elevator hatchway. Field coil 67 of motor 66 is connected through resistance 68 to mains 53 and 54 by wires 69 and 70. A control panel 71. is mounted in the motor room and all the circuit closing switches are mounted on it. The switches are all solenoid-operated and are of any well known form. Car switch 72, by which the operator controls the movements of the elevator, is mounted in the elevator car. Electromechanical brake 78 of any well-known form operates on a brake pulley (see Figure 1) attached to the shaft of armature 65.

from 7 tit) As shown in Figure 2, the elevator is at rest and generator 60 is developing the prescribed minimum voltage-corresponding to the low speed for the elevator. By movlng handle 74 of car switch72 toward the up position U, so that contact 75 covers contact 76, a circuit which starts the elevator and brings it to low speed is closed from line 54 through wires 77 and 78, solenoid soil 79 and wire 80 to line 53. The energizing of solenoid 79 opens contacts 81, 82, thus disconnecting the dynamic brake resistance 83 from across the motor armature 65. It also closes contacts 84, 85 as well as contacts 86, 87. A circuit is, therefore, established connecting motor armature 65 with generator armature 59 through wire 88, contacts 86,

' 87, wire 89,'wire 90, contacts 84, 85, wires 91 and 92, and series field 93 of generator 60. Solenoid 79 also closes contacts 94 and-95, thus completing a circuit from one side of resistance 68 through wires 96 and 97, contacts 94, 95, wires 98 and 99, branch wires 100 and 101, contacts 102, 103 and contacts 7 104, 105 which are in parallel, and wire 106, to the other side of resistance 68. This circuit short-circuits resistance 68 so that the elevator motor 66 has a full field for starting'and running at low speed. The closing of contacts 86, 87 by solenoid/79 also completes a circuit through solenoid coil 107 of the electromechanical brake 73, thereby releasing it. This circuit includes wires 63, 88, contacts 86, 87, wires 89 and 108, contacts 109, 110, resistance 83, wlres 111 and 112, coil 107 and wire 113.

By moving handle 74 of car switch 72 so that contact 75 covers both contacts 76 and 114, the elevator is brought to full speed as follows:A circuit is made fromthe mains through wire 77, contacts 75, 114, wire 115, solenoid 116, wire 117, wire'111, resistance 83, contacts 110, 109, wires 108 and 89, contacts 87 86, and wires 88 and 63. The energizing of solenoid 116 closes contacts 118, 119, contacts 120, 121 and opens contacts 102, 103. The closing of contacts 120, 121 short-circuits the resistance 62 in the generator field through wires 122 and 88, thereby permitting the generator voltage to build up.- The closing of contacts 118, 119 throws solenoid 123 across the generator terminals through wires 88 and 124, resistance 125 and series field 93. It is to be noted that solenoid 126 is shunted across the generator armature terminals at all times through a resistance 127. M

-;'-Assuming that the line voltage is 240 volts and that the minimum voltage for low "signed that solenoid 126 will actuate its speed is .40 volts, the resistance 127 is so de- .a rmature""to open contacts 104, 105 when the nerator voltage has risen to a predeter- "in'ined definite voltage, as-for example 110 Volts. Since, contacts 102, 103 have been previously opened by solenoid 116, the circuit short-circuiting resistance 68 \in the elevator motor field will be opened and a weaker field will result. The elevator motor 66 Will therefore speed up.

By suitably designing the resistance 125, the solenoid 123 may be caused to automatically close contacts 128, 129 and contacts 130, 131 at a prescribed voltage of say 200 volts. The effect of this is to connect the armature of the elevator motor directly across the mains 53 and 54 through wire 64, pontacts 129, 128, wires 92 and 91, contacts 85, 84,'wire 90, wire 89, contacts 87, 86, wires 88 and 63. At the same time, generator armature 59 is connected across the mains 53 and 54 through wire 64, contacts'131, 130, wire 132, and wire 63. Generator 60 thus becomes a motor floating on the line in parallel with driving motor 58, to which it is mechanically coupled. The object of cutting out the series field 93 by contacts 130, 131 and wire 132 is to give the motor 58 and generator 60 similar characteristics to enable thenr to operate properly'when both act as motors. In express elevator service the ability to operate the elevator motor directly from the supply mains at full elevator speed is of great advantage, since the losses in the motor-generator set are thereby kept to a minimum, amounting only to the power required to keep it turnng over. In effect, the motor-generator set is used only as a means of obtaining a definite low speed for the elevator and as a means of accelerating and retarding.

In reducing the speed of the elevator from fast speed to slow speed, the reverse operations to those just described take place and it is apparent that in coming from high speed to low speed the elevator motor will be acting as a generator and will drive the generator 60 until the voltages reach an equilibrium, thus driving motor 58, and pumping back into the mains 53 and 54.

By placing the car switch handle 7 4 in the neutral position when the elevator is running at either fast or slow speed, the solenoid 7 9 is deenergized and contacts 84, 85, contacts 86, 87, and contacts 94, 95 open. As these contacts open, contacts 81, 82 close, throwing the resistance 83 across the terminals of the armature 65 of elevator motor 66. This constitutes an electro-dynamic brake and the elevator is rapidly retarded,

the rate of retardationbeing governed by of the elevator is secured is apparent from the description above and it is also apparent that the elevator can be brought from full speed in one direction to full speed in the other direct-ion without the necessity of holding the elevator stationary longer than momentarily.

In buildings equipped with a plurality of elevators, the generators may be arranged to be mechanically driven 'from one motor. In Figure 3, two elevator motors 150 and 151 are shown with their shunt fields 152 and 153, connected to the main supply lines 154 and 155. Generator 156 supplies current for elevator motor 150 and generator 157 supplies current for elevator motor 151. Both generators 156 and 157 are driven by motor .158 and may be direct-connected thereto. The solenoid 159 is connected across the'terminals of generator 156 and in bringing the elevators to full speed as explained in connection with Figure 2, the contacts-161, 162 are automatically closed when the generator voltage reaches a predetermined value. The elevator motor 150 is then running-directly from the mains 154 and 155 and generator 156 acts as a motor and is also running directly from the mains. Since generator 156 is mechanically coupled to motor 158 and generator 157, it mayassist motor 158 in driving generator 157. Similarly, motor 151 and its generator 157 will be both directly connected to the supply mains when the elevator driven by motor 151 is running at full speed by the action of solenoid 160 and its contacts 163, 164. Although motors and generators are shown in Figure 3 for but two elevators, it will be understood that any number of generators for additional elevators, within reasonable limits, may be mechanically operated on the same principle from a common driving motor. Since under practical conditions, all elevators of a given bank are not being started simultaneously, but some are running at full speed while others are at rest, the driving motor 158 may be of considerably smaller capacity than would be required were all the generators operated by individual motors or were the elevator motors not conneeted to the supply mains at full speed. In connection with Figure 3, the details of control are not described as they will be readily understood from the description in connection with Figures 1 and 2. I have shown herein only so much of the system as is necessary to enable those skilled in the art to understand and practice the same, It will be understood that the system may be equipped with the usual safety devices such as switches for limiting the travel of the car, no voltage releases; and also other auxiliary apparatus.

l I have described my invention in connection with certain embodiments and other separately excited field for raising and low ering the elevator and a generator supplying current to the armature of the elevator motor at voltages of one polarity between a prescribed low voltage and a maximum voltage.

The minimum voltage corresponds to a de sired slow elevator speed and the maximum voltage corresponds to a desired normal full speed. The time required to build up the generator voltage from its low value to its high value determines the rate of aceeleration of the elevator. Change of direction is accomplished by reversing the current in the elevator motor armature. Another such feature resides in the use of a generator which supplies current at increasing voltage to bring the elevator motor up to a, predetermined speed, after which the motor is thrown across the line.

I claim 1. In an electric elevator system, in combination, a direct current generator having a separately excited field, a constant potential source of direct current, means for varying the excitation of said generator field to produce a minimum voltage and a maximum voltage substantially equal to the voltage of said source, a-motor for raising and lowering the elevator, connections between said generator and said elevator motor, and automatic means for connecting the armature terminals of both said elevator motor and said generator in parallel across the said source oi direct current at a-predetermined voltage.

2. In an electric elevator system, in combination, a direct current line, a directcurrent generator, a motor for raising and lowering the elevator, connections including a reversing switch between said generator. and said motor, means for varying the excitation of the generator field to produce a maximum voltage corresponding to normal fast elevator speed and a minimum voltage corresponding to slow elevator speed, and automatic means foraconnecting said elevator motor across said direct" current line at a predetermined voltage of the gem erator.

3. In an electric elevator system, in combination, a constant potential direct current line, a direct current generator, means for varying the voltage of said generator, an elev'atormotor having-a separately excited field, a resistance adapted to be inserted in the circuit of said field, means controlled by the generator voltage for inserting said re- 130 sistance at a predetermined voltage of-s'aid generator, connections including a reversing switch for supplying current from said generator to the armature of said elevator motor, and means for connecting said elevator niotoracross said constant potential direct current line.

I 4. In an-electric elevator system, in combination, a constant polarity generator, means for varying the field strength to vary the voltage at the generator terminalsbetween a minimum and a maximum voltage, a motor for raising and lowering the elevator having a separately excited field, means controlled by the generator voltage for varying the field strength of said motor, and connections between the armature terminals of said generator and said motor,

said connect-ions including switch.

5. In an electric elevator system, in combination, a constant potential direct current line, a direct current generator having a separately excited field and a series fielo, means for varying the voltage of said generator, an elevator motor, connections be tween said generator and said motor, means for connecting said generator and said elevator motor across said constant potential direct current line, and means for shortcircuiting said series field when said generatorand said elevator motor are connected across said constant potential direct current line.

GRAHAM B. GROSVENOR.

a reversing 

